From my experience, there are 3 options:
1. Transit hotel: focus is on getting 4-6 hours of sleep, thinking will be some miracle cure for your inevitable jet lag. The pool is very nice for a swim in the morning (only open 6am-12midnight) although you can just pay $SGD17 for casual use without staying. For me, this option is more to make you feel good about yourself rather than any meaningful rest and recuperation.
2. Travel into Singapore: if you’ve got 16 hours+ then you can:
a. exit customs (leaving you with 15 hours*)
b. grab a cab or other slower transport to a Singapore hotel (leaving you with 14 hours)
c. check in and connect to the wifi in your room (leaving you with 13 hours)
d. head out to a restaurant or hawker market (leaving you with 10 hours)
e. back to hotel, fart around, shower, stare at blue screen (leaving you with 8 hours)
f. hotel tells you that you have to leave hotel 3 hours before your flight (leaving you with 5 hours)
g. you know that waking up, shower, breakfast, faffing around will be an hour (leaving you with 4 hours)
3. Stay at the Crowne Plaza:
a. exit customs
b. 5 min walk to hotel
c. 20 mins and you’re into your room
d. swim in the marvellous pool
e. eat at the hotel restaurant and pay top dollar or take the elevator down to B2 and go to Changi staff restaurant and eat great food like a local for cheap as. Or do the club thing and indulge.
f. sleep in a quiet room with a super comfy bed for 8+ hours, swim, brekky, etc
g. amble into Changi and off to the lounge (it is quick to get into airport- baggage check is at each gate) with ample time and a zen feel
* times elaborated somewhat for dramatic tension